The present invention relates to a lubricating device for an engine. In particular, the present invention relates to a lubricating device for an engine in which a relief valve is anchored to a rotor plate.
An engine oil pump takes up and pressurizes oil from an oil pan. The pressurized oil is delivered in the area to be lubricated. An oil passageway receiving pressurized oil from the oil pump includes a relief valve which maintains the oil pressure in the oil passageway at a predetermined value.
In general, a relief valve is held in the closed position by a spring until the pressure in the relief passageway exceeds a setpoint. At higher oil pressures, the relief valve is opened to relieve the excess pressure.
An example of a lubricating device for an engine is disclosed in laid-open Japanese utility model publication number 3-51156. A crank case lower half frame of an engine making up the lower half of a crank case of an engine has a front wall, a middle wall box, and a back wall, all placed between right and left side walls. These side walls are constructed as a single body to form the crank case lower half frame. On the lower end of each of the front wall, wall box, and back wall, there is a reinforcement plate attachment surface. An oil retaining/reinforcement wall is placed against the reinforcement plate attachment surface and is fastened by fastening means in a manner that permits disassembly.
Referring to FIG. 5, an engine 102 of the prior art includes a lower case 106. A rotor plate 108 and a chain case 110 are disposed on the front side of engine 102. Rotor plate 108 is anchored to the back of chain case 110 by an anchoring bolt which is not shown.
Rotor plate 108 and chain case 110 are disposed on a first journal bearing 114 of lower case 106. The front side of front journal bearing 114 of lower case 106 is flat. A relief valve 116 is integrated into the front of front journal bearing 114 and one end (the right side in FIG. 5) of rotor plate 108. Relief valve 116 is anchored to the front of first journal bearing 114 slightly forward of front journal bearing 114. The forward placement of relief valve 116 avoids interference with front journal bearing 114.
The above arrangement provides a thickness of chain case 110 equal to L1. This arrangement increases the overall length of the engine. This is a disadvantage in practical applications.
Because thickness L1 of chain case 110 is large, the weight of chain case 110 is also large. As a consequence, engine 102 is heavier than desired.
Furthermore, excess oil relieved from relief valve 116 is relieved in front of front journal bearing 114 on lower case 103 which is formed flat. The excess oil tends to splash, thereby complicating smooth oil recovery. Splashing aerates the oil, which carries danger of reduced performance.